<!DOCTYPE html>
<html>
      <head>
            <meta charset="utf-8">
            <meta name="viewport" content="width=device-width,initial-scale=1">
            <title>加载中</title>
            <link rel="stylesheet" href="https://cdn.staticfile.net/twitter-bootstrap/4.3.1/css/bootstrap.min.css">
            <script src="https://cdn.staticfile.net/jquery/3.2.1/jquery.min.js"></script>
            <script src="https://cdn.staticfile.net/popper.js/1.15.0/umd/popper.min.js"></script>
            <script src="https://cdn.staticfile.net/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script>
      </head>
      <body>
            <!-- 不同颜色的加载中 -->
            <div class="spinner-border text-muted"></div>
            <div class="spinner-border text-primary"></div>
            <div class="spinner-border text-success"></div>
            <div class="spinner-border text-info"></div>
            <div class="spinner-border text-warning"></div>
            <div class="spinner-border text-danger"></div>
            <div class="spinner-border text-secondary"></div>
            <div class="spinner-border text-dark"></div>
            <div class="spinner-border text-light"></div>

            <!-- 闪烁的加载效果 -->
            <div class="spinner-grow text-muted"></div>
            <div class="spinner-grow text-primary"></div>
            <div class="spinner-grow text-success"></div>
            <div class="spinner-grow text-info"></div>
            <div class="spinner-grow text-warning"></div>
            <div class="spinner-grow text-danger"></div>
            <div class="spinner-grow text-secondary"></div>
            <div class="spinner-grow text-dark"></div>
            <div class="spinner-grow text-light"></div>

            <!-- spinner-border-sm 和spinner-grow-sm 设置加载效果大小 -->
            <div class="spinner-border spinner-border-sm text-muted"></div>
            <div class="spinner-grow spinner-grow-sm text-muted"></div>
      </body>
</html>